Chest Compression Belt with Belt Position Monitoring System

ABSTRACT

An automated chest compression device for performing CPR, with distance sensors disposed on a compressing mechanism and on a structure fixed relative to the CPR patient, for determining inferior/superior movement of the compressing mechanism over the course of multiple compressions.

This application claims priority to U.S. Provisional Application61/654,642 filed Jun. 1, 2012.

FIELD OF THE INVENTIONS

The inventions described below relate to the field of CPR chestcompression devices.

BACKGROUND OF THE INVENTIONS

Cardiopulmonary resuscitation (CPR) is a well-known and valuable methodof first aid used to resuscitate people who have suffered from cardiacarrest. CPR requires repetitive chest compressions to squeeze the heartand the thoracic cavity to pump blood through the body. Artificialrespiration, such as mouth-to-mouth breathing or a bag mask apparatus,is used to supply air to the lungs. When a first aid provider performsmanual chest compression effectively, blood flow in the body is about25% to 30% of normal blood flow. However, even experienced paramedicscannot maintain adequate chest compressions for more than a few minutes.Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successfulat sustaining or reviving the patient. Nevertheless, if chestcompressions could be adequately maintained, then cardiac arrest victimscould be sustained for extended periods of time. Occasional reports ofextended CPR efforts (45 to 90 minutes) have been reported, with thevictims eventually being saved by coronary bypass surgery. See Tovar, etal., Successful Myocardial Revascularization and Neurologic Recovery, 22Texas Heart J. 271 (1995).

In efforts to provide better blood flow and increase the effectivenessof bystander resuscitation efforts, various mechanical devices have beenproposed for performing CPR. In one variation of such devices, a belt isplaced around the patient's chest and the belt is used to effect chestcompressions. Our own patents, Mollenauer, et al., Resuscitation DeviceHaving A Motor Driven Belt To Constrict/Compress The Chest, U.S. Pat.No. 6,142,962 (Nov. 7, 2000); Sherman, et al., CPR Assist Device withPressure Bladder Feedback, U.S. Pat. No. 6,616,620 (Sep. 9, 2003);Sherman, et al., Modular CPR assist device, U.S. Pat. No. 6,066,106 (May23, 2000); and Sherman, et al., Modular CPR assist device, U.S. Pat. No.6,398,745 (Jun. 4, 2002), show chest compression devices that compress apatient's chest with a belt. Each of these patents is herebyincorporated by reference in their entirety. Our commercial device, soldunder the trademark AUTOPULSE®, is described in some detail in our priorpatents, including Jensen, Lightweight Electro-Mechanical ChestCompression Device, U.S. Pat. No. 7,347,832 (Mar. 25, 2008) andQuintana, et al., Methods and Devices for Attaching a Belt Cartridge toa Chest Compression Device, U.S. Pat. No. 7,354,407 (Apr. 8, 2008).

These devices have proven to be valuable alternatives to manual CPR, andevidence is mounting that they provide circulation superior to thatprovided by manual CPR, and also result in higher survival rates forcardiac arrest victims. The AUTOPULSE® CPR devices are intended for usein the field, to treat victims of cardiac arrest during transport to ahospital, where the victims are expected to be treated by extremelywell-trained emergency room physicians. The AutoPulse® CPR device isuniquely configured for this use: All the components are stored in alightweight backboard, about the size of a boogie board, which is easilycarried to a patient and slipped underneath the patient's thorax. Theimportant components include a compression belt, motor, drive shaft anddrive spool, computer control system and battery.

Addressing another aspect of CPR, chest compression monitoring duringthe course of CPR is now possible with the Real CPR Help® technologymarketed by ZOLL Medical Corporation. This technology is described inU.S. Pat. Nos. 6,390,996, 7,108,665, and 7,429,250, and includes the useof an accelerometer to measure accelerations of the chest andcalculating the depth of each compression from the acceleration signal.The technology is used in ZOLL's Real CPR Help® compression depthmonitoring system to provide real-time rate and depth CPR feedback formanual CPR providers. Commercially, it is implemented in ZOLL'selectrode pads, such as the CPR-D•padz® electrode pads. It is alsoimplemented for training use in the iPhone app PocketCPR®. The sametechnology can be provided in automatic CPR chest compression devices,such as ZOLL Circulation's AutoPulse® chest compression device, which isdescribed in numerous patents issued to ZOLL Circulation such as U.S.Pat. No. 6,066,106 and its continuations. U.S. Pat. Nos. 6,390,996,7,108,665, and 7,429,250 also propose use of compression depthmonitoring in combination with an automatic constricting devicedescribed in U.S. Pat. No. 4,928,674, which is an inflatable vestoperable to squeeze the chest of a patient repeatedly to provide CPRchest compressions.

The Real CPR Help® compression depth monitoring system provides valuableunambiguous feedback during manual CPR, because the accelerometer isfixed to the chest of the patient either because is it fixed toelectrode pads that are fixed to the patient's chest with adhesive, orbecause it is fixed relative the CPR providers hands which the CPRprovider maintains in the appropriate location over the sternum of thepatient. Chest compression information that might be provided duringautomated CPR with the AutoPulse® device may be unambiguous, assumingthat the compression belt used with the AutoPulse® device does not shiftduring the course of treatment. While this may be monitored visually byan EMT using the AutoPulse®, the system can be improved by providingsome mechanism for determining compression depth in the case where thecompression belt shifts up or down on the patient's chest during use.

During the course of automated chest compression using the AutoPulse®chest compression device, CPR providers using the device may beconcerned about inferior/superior movement of the belt. The device maybe operated for several minutes, including time moving the patient intoan ambulance, transporting the patient to a hospital, and moving thepatient from the ambulance and into a hospital emergency room. With allthis movement, it is possible that the compression belt might moveeither upward toward the patient's shoulders (superiorly, relative tothe patient), or downward toward the patient's abdomen (inferiorly,relative to the patient). None of the references discussed above providea means for detecting horizontal displacement or non-uniformity in thedownward movement of a compression component of an automated chestcompression device.

SUMMARY

The devices and methods described below provide for continuousmonitoring of the inferior/superior position of a compression belt of aCPR compression device and continuous monitoring of the uniformity ornon-uniformity of the downward movement of a compression belt. In onesystem described below, this is accomplished with a compression beltfitted with markers, which may be active signal emitters or passivesignal reflectors, together with a plurality of signal detectors on astructure which is fixed relative to the patient (or, conversely,markers fixed relative to the patient in combination with signaldetectors secured on the belt). In reference to the AutoPulse®, whichuses a load distributing panels as components of a compression belt (nowcommonly referred to as a load distributing band) that is disposed overthe chest of the patient during use, the markers or signal detectors maybe disposed on the load distributing panels.

Movement of the belt-mounted component is tied to movement of the loaddistributing band or a portion of the load distributing band. Assumingthat the fixed components (the housing or a separate support gantry) areheld fixed relative to the patient's main mass (but not the chestcomponents (sternum, anterior portions of the ribs) that are compressedby the compression belt), anterior/posterior movement of the loaddistributing band relative to the main mass of the patient, andinferior/superior movement (up and down, relative to the patient'sbody), can be detected and measured.

Anterior/posterior movement can be measured to determine depth ofcompression, and that measurement can be used to confirm propercompression and/or adjust compressions accomplished automatically by theCPR compression device. Superior/Inferior movement can be measured toconfirm proper positioning of the compression belt or load distributingpanels of the belt. Detection of inferior/superior movement, or lack ofmovement, can be used to determine improper placement, or confirm properplacement, of the compression belt or load distributing panels along thesuperior/inferior axis of the patient.

The detector/emitter system can work on several principles. Suchdetectors may be ultrasonic distance sensors, with corresponding markerscomprising reflective surfaces, optical sensors, RFID sensors, ormagnetic sensors. Using two detectors space apart from each other, andbasic triangulation, the relative location of the belt-mounted componentvis-à-vis the fixed components can be determined. A computer controlsystem can be used in the conjunction with the emitter/detector systemto calculate the location of the belt-mounted component vis-à-vis thefixed components, and determine desired and undesired movement of thecompression belt. Proper depth of compression, inadequate or excessivecompression, and inferior/superior slippage of the compression belt orload distributing panels, and even changes of the patient's chest causedby the compressions can be detected. In addition, spontaneous chestmovements, or movements cause by ventilation, can be identified andmeasured.

A second system and method described below provides for continuousmonitoring of the inferior/superior position of a compression belt of aCPR compression device and continuous monitoring of the uniformity ornon-uniformity of the downward movement of a compression belt using acompression belt fitted with one or more accelerometers operable todetect horizontal movement of the compression belt, and a microprocessoror control system which interprets signals from the accelerometer(s) todetermine horizontal movement of the belt. In reference to theAutoPulse®, which uses load distributing panels as components of acompression belt that is disposed over the chest of the patient duringuse, accelerometers may be disposed on the load distributing panels.

Movement of the belt-mounted accelerometer is tied to movement of theload distributing band or a portion of the load distributing band.Assuming that the fixed components are held fixed relative to thepatient's main mass (but not the chest components that are compressed bythe compression belt), anterior/posterior movement of the loaddistributing band relative to the main mass of the patient, andinferior/superior movement (up and down, relative to the patient'sbody), can be detected and measured. Anterior/posterior movement can bemeasured to determine depth of compression, as proposed in U.S. Pat. No.6,390,996 and that measurement can be used to confirm proper compressionand/or adjust compressions accomplished automatically by the CPRcompression device. In addition, superior/inferior movement can bemeasured to confirm proper positioning of the compression belt or loaddistributing band. Detection of inferior/superior movement, or lack ofmovement, can be used to determine improper placement, or confirm properplacement, of the compression belt or load distributing band along thesuperior/inferior axis of the patient. In addition, anterior/posteriormovement can be measured to confirm uniform downward motion of thecompression belt or load distributing band. Detection of uniformanterior/posterior movement, or non-uniform anterior/posterior movement,can be used to confirm proper downward movement, or determine improperdownward movement, of the compression belt or load distributing band.

With the information gained regarding the position of the belt-mountedcomponent, the position of the belt and depth of compressions caused bythe belt are calculated by the control system. The operation of thechest compression belt can be modified in response to the information.The compression belt operation can be adjusted, in response to theinformation gained. For example, the system may interrupt compressionsif significant slippage is detected, and/or notify an EMT or other CPRprovider that the compression belt has slipped out of place. The systemmay also be used to detect changes in chest compliance (which might becaused by airway blockage, natural remodeling of the chest over thecourse of treatment, or iatrogenic injury) and notify the CPR providerof significant changes. The system may also be used to control the chestcompression belt operation so as to reach a specified depth ofcompression, or to interrupt compressions if ventilation or naturalrespiration is reflected in the position data.

The inventions described above can be used to perform CPR withparameters which vary according to the patient's shape, as determined bythe distance sensors. The distance sensors can be used to determine thesize and shape of the patient's chest, and the control system can thenalter the compression depth to account for differing physiology such asflat or barrel chested patients. The distance sensors and/or theaccelerometers, combined with measurements of chest compliance orresilience, can be used by the control system to determine therelationship between the compression depth achieved and the forceapplied to the chest, and adjust the target compression depth when therelationship suggest that chest compliance has increased due to breakageof the patient's ribs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a chest compression belt fitted on a patient.

FIG. 2 is a schematic cross section of the chest compression device ofFIG. 1.

FIG. 3 shows a chest compression belt fitted on a patient, with a pairof emitter/detector arrays disposed about the chest compression device.

FIG. 4 is a schematic cross section of the chest compression device ofFIG. 3.

FIG. 5 is a schematic cross section of a chest compression devicesimilar to that of FIG. 3, with one array disposed on posts disposed onthe chest compression device.

FIG. 6 is a schematic cross section of the chest compression device ofFIG. 5.

FIG. 7 is a schematic cross section of a chest compression devicesimilar to that of FIG. 3, with one array disposed in the housing of theCPR compression device.

FIG. 8 is a schematic cross section of a chest compression devicesimilar to that of FIGS. 3 through 7, with an additionalemitter/detector disposed on the patient's body.

FIG. 9 shows a chest compression belt fitted on a patient.

FIG. 10 is a longitudinal cross section of the chest compression deviceof FIG. 9.

FIG. 11 is a longitudinal cross section of the chest compression deviceof FIG. 9.

FIG. 12 is a longitudinal cross section of the chest compression deviceof FIG. 9.

FIGS. 13 and 14 illustrate the application of the system of motiondetection applied to a piston based chest compression device.

FIGS. 15 and 16 illustrate the application of the chest compressiondevice to patients with varying thoracic cross-sections.

FIG. 17 illustrates use of the chest compression device in combinationwith the distance sensors and an adjustable bladder disposed between thecompression belt and the patient.

FIG. 18 illustrates a system similar to that of FIGS. 9 and 10, with theadditional features to detect changes in chest resilience.

FIG. 19 is a graph illustrating the relationship between chestresilience and compression depth.

DETAILED DESCRIPTION OF THE INVENTIONS

FIGS. 1 and 2 illustrate the chest compression device, similar to theAutoPulse® CPR chest compression device, fitted on a patient 1. A chestcompression device 2 applies compressions with the belt 3, which has aright belt portion 3R and a left belt portion 3L, including loaddistributing panels 4R and 4L designed for placement over the anteriorsurface of the patient's chest while in use, and tensioning portionswhich extend from the load distributing portions to a drive spool, shownin the illustration as narrow pull straps 5R and 5L. (The entirety ofthe compression belt is referred to as a “load distributing band” in theart.) The right belt portion and left belt portion are secured to eachother with hook and loop fasteners and aligned with the eyelet 6 andprotrusion 7. A bladder 8 is disposed between the belt and the chest ofthe patient. The narrow pull straps 5R and 5L of the belt are spooledonto a drive spool located within the platform (shown in FIG. 2) totighten the belt during use, passing first over laterally locatedspindles 9L and 9R. The chest compression device 2 includes a platform10 and a compression belt cartridge 11 (which includes the belt). Theplatform includes a housing 12 upon which the patient rests. Means fortightening the belt, a processor and a user interface are disposedwithin the housing. In the commercial embodiment of the device, themeans for tightening the belt includes a motor, a drive train (clutch,brake and/or gear box) and a drive spool upon which the belt spoolsduring use.

FIG. 2 is a schematic cross section of the device of FIG. 1, installedon a patient 1. The components include the compression belt 3L and 3R,the load distribution portions of the belt 4L and R, the narrow strapportions 5L and R, the bladder 8, the spindles 9L and R. The drive spool13 and the spline 14 which fixes the belt to the drive spool are locatedwithin the housing 12, as is a motor and computer control system whichoperate to drive the drive spool to spool the belt, thereby tighteningthe belt about the chest and thorax of the patient and a resuscitativerate to accomplish CPR. A load plate 15 is disposed on the platform (theupper surface of the housing). The anatomical landmarks shown in thisFigure include the sternum 16, the spine 17, and the right and leftscapula 18R and 18L of the patient. Referring to the landmarks, thechest compression band is wrapped around the patient such that the loaddistributing portions are located on the chest (that is, the anteriorsurface or portion of the thorax), over the sternum, with the narrowstrap portions descending from the load distributing portions to wraparound the lateral spindles and thence run to the drive spool. Thelateral spindles are spaced laterally from the medial centerline of thedevice so that they are disposed under, or lateral to, the scapulae ofthe typical patient, so that tightening of the compression band resultsin anterior/posterior compression of the chest. In use, the patient mustremain fixed relative to the housing: That is, some anatomical parts ofthe patient must remain in substantially fixed relation to the housingwhile the sternum is compressed toward the spine. In practice, we findthat the spine and scapula remain fixed, or nearly fixed, relative tothe platform while the sternum and anterior portions of the thorax arecompressed downwardly toward the spine, the scapula, and the housing.

Our experience with the belt suggests that it is desirable to monitorthe position of the belt during CPR. Our compression depth monitor,describe in our Patent U.S. Pat. Nos. 6,390,996, 7,108,665, and7,429,250, and commercialized under the Real CPR Help® trademark, can beused to provide feedback regarding the depth of compressions, which is acritical parameter for CPR. However, it is desirable to automaticallydetect slippage of the belt along the inferior/superior axis of thesystem, which would indicate that the belt has slipped up or down on thepatient, or that the patient has moved or changed shape. Slipping can becaused by the interaction of forces applied by belt on the patient.Shape changes that effect the application of CPR can occur as a resultof natural remodeling of the chest during the course of treatment. Thesystem described in relation to FIGS. 3 and 4 can provide thisinformation, and can also provide information regarding theinferior/superior motion of the compression belt.

As shown in FIGS. 3 and 4, and array assembly of emitter/detectorscomponents is disposed about the patient, over the compression belt, andan array of detector/emitter components is arranged on the compressionbelt. The array assembly includes multiple emitter/detectors 19 arrangedon a support structure 20 over the patient and the compression belt. Thesupport structure of FIGS. 3 and 4 is sized and dimensioned to fit overthe chest of the patient, over the compression belt, and may be fixed tothe housing of the compression device. A second array assembly may bemade up of the compression belt itself, along with multipleemitter/detectors 21 disposed on the belt. One or both of the sensorarrays may be operably connected to a computer (of any form) which maycontrol operation of the emitter/detector components, accept signalsprovided from the emitter/detector components, analyze the signals andcalculate from those signals the position of the emitter/detectorcomponents on the compression belt. The computer may be part of, orseparate from, the computer that directly controls the CPR compressiondevice. Depending on the emitter/detector technology, a second array maybe unnecessary, and the desired distance measurements can beaccomplished with a single array mounted on the support structure or thebelt. Where, for example, ultrasonic distance sensors are used toimplement the system, the emitter/detectors 21 can be replaced withdetectable markers, or ultrasonic reflectors. Where, for example,optical sensors are used, the laser and camera components may be mountedon the gantry, and markers (reflectors) may be disposed on the belt (thebelt itself may serve as the reflective surface).

The support structure may take various forms suitable for holding theemitter/detectors 19 spatially fixed relative to the housing of thecompression device. FIG. 5 illustrates a chest compression devicesimilar to that of FIG. 3, with one array disposed on posts disposed onthe chest compression device. FIG. 6 is a schematic cross section of thechest compression device of FIG. 5. The compression device componentsinclude the housing 12, the compression belt 3L and 3R, the loaddistribution portions of the belt 4L and R, the narrow strap portions 5Land 5R, the bladder 8, the spindles 9L and R illustrated previously. Theemitter/detectors 19 are disposed on support structure comprising posts22L and 22R. The posts are mounted on the housing 12, extendingvertically upwardly from the housing, on either side of the patient, inthe area corresponding to the axillae of the patient when the device isinstalled on a patient. The mechanical posts may be approximately 6inches (15 cm) in height and 1 inch (2.5 cm) in diameter. Duringpositioning of the patient on the housing 12, the patient is positionedsuch that the posts rest in or near the patient's axillae (armpits). Theposts provide a secondary benefit of providing an easy guide forpositioning the patient onto the board. The posts may fold down intorecesses in the housing during transport and storage of the compressiondevice, and may be raised after a patient has been placed on the board.The posts can raised manually or mechanically.

FIG. 7 is a schematic cross section of a chest compression devicesimilar to that of FIG. 3, with one array disposed in the housing of theCPR compression device. In this Figure, the components are similar tothe components of the chest compression device of FIGS. 3 and 4,including the compression belt 3L and 3R, the load distribution portionsof the belt 4L and 4R, the narrow strap portions 5L and R, the bladder8, the spindles 9L and 9R, the drive spool 13 and the spline 14 whichfixes the belt to the drive spool 15 within the housing 12, and the loadplate 15 on the platform. The anatomical landmarks, including thesternum 16, the spine 17, and the right and left scapula 18R and 18L arealso shown in the Figure. A first array of emitter/detectors 23 aredisposed in or on the housing, and may be dispersed both across thewidth of the housing (the medial/lateral axis of the patient and thedevice) and the length or height of the housing (corresponding to theinferior/superior axis of the patient). If necessary, a second array ofemitter/detectors 24 are disposed in or on the compression belt, and maybe dispersed both across the width of and length of the belt. Theemitter/detectors 24 (the array on the belt) would be matched to theemitter/detectors 23 on the housing. Depending on the technology used toimplement the distance measurement, emitter/detectors on the belt mayused with a corresponding array on the housing, provided that theemitter detectors on the belt can use pre-existing structure on thehousing 12, such as the upper surface. Also, depending on the technologyused to implement the system, the emitter/detectors 24 can be replacedwith detectable markers, or reflectors. Likewise, pre-existingstructures on the belt may be used in conjunction with an array ofemitter/detectors on the housing to provide the necessary reflectivesurfaces for some distance sensors.

FIG. 8 is a schematic cross section of a chest compression devicesimilar to that of FIGS. 3 through 6, with an additional body-mountedemitter/detector 28 disposed on the patient's body. As withemitter/detectors 21, emitter/detector 28 is interoperable withemitter/detectors 19 or 23 to determine the position of the body-mountedemitter/detector and emitter/detectors fixed relative to the housing.The emitter/detector can be placed directly on the patient, near thesternum and inferior to the bladder 8, and additional body-mountedemitter/detectors can be placed laterally on the patient's rib cage orabdomen. The body-mounted emitter/detector can be incorporated intodefibrillator electrode pads, which will typically be placed on thepatient before the compression device is applied to the patient. Usingthe emitter/detector 28 with emitter/detectors 19 or 23, the controlsystem can be operated to detect large undesirable changes in theposition of the patient relative to the housing, as might occur duringtransport of the patient down stairs, over rugged terrain, or in anambulance.

The detector/emitter system can work on several principles. Non-contactultrasonic distance sensors (such as those described in U.S. Pat. No.6,690,616) may be used. In this embodiment, ultrasonic emitter/detectors(components that emit ultrasound and detect ultrasound reflected fromnearby objects) are disposed on the support structure. Ultrasonicdistance measurement can be accurate to 0.05%. RF Near Object Detectiontechnology can be employed (such as described in U.S. Pub.2002/0147534). Optical distance sensors can be employed, which use laseremitters and optical detectors which may be closely spaced on the gantryor posts, and direct laser light onto the compression belt surface, orspecially applied reflectors and detect the reflected laser light.Magnetic motion sensors, such as those which use an electromagneticsource and sensor, described in Geheb, et al., Method and Apparatus forEnhancement of Compressions During CPR, U.S. Pat. No. 7,220,235 (May 22,2007) and Centen, et al., Reference Sensor For CPR Feedback Device, U.S.Pub. 2012/0083720 (Apr. 5, 2012), may also be used. These technologieswill be sufficient to calculate the depth of compression accomplished bythe compression belt.

To determine slippage, or inferior/superior movement of the beltrelative to the patient, the arrays can use three detectors on thesupport structure, where the detectors define a plane (so that they arenot arranged in a straight line), and at least one emitter on thecompression belt, at a location that most closely conforms to themovement of the chest. Using basic triangulation calculations based onthe measured distance from each detector to the emitter, the position ofthe emitter, and thus the belt, can be calculated. In this manner, achange of the position of the belt-mounted emitter out of the planeestablished by the three detectors can be interpreted as aninferior/superior movement of the compression belt, or inferior/superiortilting of the belt.

The computer that interprets the data obtained from the sensor arrays isprogrammed to track motion of the sensors on the belt, and interpretthis as belt position. This data can be processed by the computer todetermine the depth of compression provided by the belt, and determinesuperior/inferior motion of the belt during the course of compressions.Upon initiation of the system in a resuscitation attempt, the systemwill determine the initial position of the belt, relative to theemitter/detectors/markers of the support structure or housing. Thesystem may assume that initial placement is correct, or prompt anoperator for confirmation that placement is as desired by the operator.(With addition of an emitter/detector/marker on the belt and thehousing, the system can also confirm that the array, belt and housingare all properly aligned on the anterior/posterior axis of the system.)Thereafter, the computer system interprets the data obtained from thearrays, which provide data corresponding to the distance between emitterdetectors on corresponding arrays, to determine any inferior/superiordrift of the belt. Referring to the additional emitter/detector shown inFIG. 8, the computer is programmed to track motion of the sensors on thesupport structure or housing, and interpret this as the patientposition. This data can be processed by the computer to determine themovement of the patient relative to the support structure or housing.Upon initiation of the system in a resuscitation attempt, the systemwill determine the initial position of the patient relative to thesupport structure or housing. The system may assume that initialplacement is correct, or prompt an operator for confirmation thatpatient placement is as desired by the operator. Thereafter, thecomputer system interprets the data obtained from the arrays, whichprovide data corresponding to the distance between emitter detectors oncorresponding arrays, to determine if the patient has moved relative tothe support structure or housing.

In response to detected inferior/superior movement of the belt whichexceed a predetermined limit, the computer which controls the CPRcompression device can direct operation of the device to take one ormore of the following actions: (1) suspend compressions until reset by aCPR provider (2) provide prompts to a CPR provider to indicate the factthat slippage has been detected and/or (3) adjust depth of compressionor compression rate, or adjust the compression waveform to account forthe slippage while still providing compression. Currently, thepredetermined limit for inferior movement (downward movement, relativeto the patient's anatomy, such as movement toward the abdomen) should beabout 0.5″ to 1″ (1.25 to 2.5 cm), while the predetermined limit forsuperior movement (upward movement, relative to the patient's anatomy,such as movement toward the head of the patient) should be about 0.5″ to1″ (1.25 to 2.5 cm), for belts used in the AutoPulse® chest compressionsystem. Expressed in terms of the patient's anatomy, motion of a portionof the belt below the xiphoid process, or motion of a portion of thebelt above the sternal notch, may be used to establish predeterminedlimits. Thus, disposing a component of the emitter/detector pair on thesuperior or inferior edges of the band, or aiming the opticalemitter/detector to the superior or inferior edges of the band, anddetermining the average distance from the edge of the band and theanatomical landmark in the average initial placement of the band, thepredetermined limit can be expressed as 0.5″ (1.25 cm) below the xiphoidprocess or above the sternal notch of the patient.

In response to detected compression depth, the computer which controlsthe CPR compression depth can increase or decrease the amount ofcompression applied to the patient, by increasing or decreasing theamount of the belt spooled on the drive spool. Also, the computer candirect operation of the device to (1) suspend compressions until resetby a CPR provider (2) provide prompts to a CPR provider to indicate thefact that compression depth is excessive or inadequate and/or (3) adjustdepth of compression to accomplish compression to the desired depth of1.5 to 2 inches (3.75 to 5 cm), and/or (4) adjust the compression waveform or compression rate.

In response to detected displacement of the patient relative to thesupport structure or housing, the computer which controls the CPRcompression depth can direct operation of the device to (1) suspendcompressions until reset by a CPR provider and (2) provide prompts to aCPR provider to indicate the fact that unacceptable patient movement hasbeen detected and/or (3) adjust depth of compression to accomplishcompression to a depth of lesser than or greater than the recommended1.5 to 2 inches (3.75 to 5 cm), and/or (4) adjust the compression waveform or compression rate.

FIGS. 9 and 10 illustrate the chest compression device, similar to theAutoPulse® CPR chest compression device, fitted on a patient 1. Thechest compression device 2, belt 3 with right belt portion 3R and a leftbelt portion 3L, distributing portions 4R and 4L and narrow pull straps5R and 5L and other components are as described above in relation toFIG. 1. Accelerometers 29 and 30 are disposed on the belt, located alongthe inferior/superior axis of the belt. As illustrated, theaccelerometers are disposed on a load distributing panel. Theaccelerometers, along with the control system and appropriateprogramming, can be used to detect acceleration of the belt along theinferior/superior axis and the anterior/posterior axis (as well as thetransverse, left-to-right axis) of the patient, and determine thedistance traveled by the belt, and different portions of the belt, alongboth the inferior/superior axis and the anterior/posterior of the axisof the patient. The control system is further programmed such that, upondetection of undesirable movement (either excessive movement ornon-uniform movement) the control system operates a display associatedwith the compression device to warn an operator, and/or suspendcompression operation of the device, and/or change the depth ofcompression and/or adjust the compression wave form or compression rate.

FIG. 10 is a side view of the device of FIG. 9, installed on a patient1. The components are as describe in relation to the previous Figures,and include the compression belt 3L and 3R, the load distributionportions of the belt 4R and 4L, the narrow strap portions 5R and 5L, thebladder 8, the spindles 9L and 9R, the drive spool 13, the spline 14 andthe load plate 15. The anatomical landmarks shown in this Figure includethe sternum 16 and the spine 17. Referring to the landmarks, the chestcompression band is wrapped around the patient such that the loaddistributing portions are located on the chest (that is, the anteriorsurface or portion of the thorax), over the sternum, with the narrowstrap portions descending from the load distributing portions to wraparound the lateral spindles and thence run to the drive spool. Asdescribed in relation to FIG. 2, the lateral spindles are spacedlaterally from the medial centerline of the device so that they aredisposed under, or lateral to, the scapulae of the typical patient (seeFIG. 2), so that tightening of the compression band results inanterior/posterior compression of the chest.

FIGS. 11 and 12 are longitudinal cross sections of the chest compressiondevice of FIGS. 9 and 10, demonstrating the types of belt slippage andmovement that the system is intended to detect. In FIG. 11, the belt hasmoved horizontally, along the inferior/superior axis of the housing andthe patient. This horizontal movement is undesirable, because the systemassumes that the patient is positioned relative to the housing such thatthe load distributing portion of the belt, when in its original positioncentered over the drive spool and load plate, is also properly locatedover the chest (the anterior surface of the thorax) of the patient, andthus the narrow strap portions of the belt are aligned vertically (asclose a possible to vertically) so that the tension applied through thenarrow straps is directed substantially entirely alonganterior/posterior axis (front to back, or straight downward wheninstalled on a supine patient), rather than pulling inefficiently alongthe inferior/superior axis.

In FIG. 12, the belt, and specifically the load distributing portion ofthe belt, has become tilted upon tightening of the belt, in the sensethat the inferior extent of the load distributing portion moves furtherdownward during a compression than does the superior extent of the loaddistributing portion. Extreme non-symmetrical movement of the belt isundesirable because it is unexpected assuming that the belt is properlypositioned such that the load distributing portion of the belt, when inits original position centered over the drive spool and load plate, isalso properly located over the chest (the anterior surface of thethorax) of the patient, so that the load distributing portion isdisposed over the sternum and acts on the patient's rib cage. Extremenon-uniform or non-symmetrical anterior-to-posterior movement of thebelt, in the sense that the top (superior portion) of the belt movesposteriorly either more or less than the bottom (inferior portion) maybe a sign that the belt has moved, relative to the patient, such thatthe inferior portion is impinging on the patients abdomen, or that thebelt is encountering some interference. It could also be a sign that thepatient's thorax has changed significantly in its response tocompressions. Changes could be due to rib breakage, sternum breakage, ornormal response to repeated chest compressions.

Using the techniques disclosed in our prior patents for determiningchest compression depth with or without reference to fixed referencesensors, the accelerometers can readily be used to provide accelerationdata regarding horizontal inferior/superior movement of the belt and/ortransverse motion of the belt. Using readily available three-axisaccelerometers, chest compression depth at various points long theinferior/superior axis of the belt can also be determined.

With an accelerometer fixed to the load distributing portion of thebelt, preferably near the centerline of the patient, an accelerometersignal corresponding to the inferior/superior position of the belt,relative to its initial placement, can be obtained. Because use of theCPR chest compression device requires human operators for placement andinitiation of the system, the initial position of the belt can beassumed to be a correct position, and the position detecting system canbe used to monitor movement using the stationary accelerometer data uponstartup as a starting point for calculating movement. Alternatively,because we are concerned with motion of the belt relative to thepatient's chest, and assume that the patient is substantially fixedrelative to the housing, a reference accelerometer disposed on thehousing can also be used to detect overall movement of the housing, andthe signals of the housing mounted accelerometer and the belt-mountedaccelerometer may be combined (subtracted) to determine movement of thebelt vis-à-vis the housing.

To detect inferior/superior movement of the belt, the accelerometer iscoupled to the compression belt with an axis of acceleration sensitivity(the term of art used by accelerometer makers) aligned with theinferior/superior axis of the belt (which corresponds to theinferior/superior axis of the housing and the patient). To detectanterior/posterior movement of the belt, the accelerometer is coupled tothe compression belt with an access of acceleration sensitivity (theterm of art used by accelerometer makers) aligned with theanterior/posterior axis of the belt (which corresponds to theanterior/posterior axis of the housing and the patient). If a three-axisaccelerometer (that is, three accelerometers arranged orthogonally,within a single device) is used, the remaining axes can be used also, toprovide acceleration data related to left to right motion, of the belt.An Analog Devices ADXL345 three-axis digital accelerometer, which isused in our PocketCPR® device, may be used in the device described here,and an Analog Devices ADXL321 two-axis accelerometer, or two ADXL103single-axis accelerometers may also be used. The inferior/superioraccelerometer is operated to provide acceleration signals to themicroprocessor (the computer used to interpret the acceleration data maybe the same computer that controls the chest compression operation ofthe device, or a separate microprocessor or computer), and the controlsystem is programmed to calculate, based on the acceleration signal, theinferior/superior distance over which the accelerometer moves from itsoriginal location. The anterior/posterior accelerometer is operated toprovide acceleration signals to the microprocessor (the computer used tointerpret the acceleration data may be the same computer that controlsthe chest compression operation of the device, or a separatemicroprocessor or computer), and the control system is programmed tocalculate, based on the acceleration signal, the anterior/posteriordistance over which the accelerometer moves from its original location.(While it is preferred to align the axes of acceleration sensitivitywith the axes of the patient, it is not necessary, but the accelerationsignal provided by the accelerometer is strongest along its axis ofacceleration sensitivity. Misalignment can be accounted for throughcalculations to obtain suitable distance determinations.)

Upon initiation of the chest compression device, the accelerometershould be stationary in the inferior/posterior plane and theanterior/posterior plane, and thus the accelerometer(s) should beoutputting a signal indicating zero acceleration and velocity. Prior toinitiation of compressions, the control system, through the display onthe device, or through a speaker, prompts the user to confirm properplacement of the belt. Upon user input (push of a start button (physicalor touch screen) or keyboard command, or other input), the controlsystem initiates compression belt operation to accomplish a series ofrepeated tightening and loosening of the belt about the thorax of thepatient. The control system is programmed with the assumption that thisposition is an acceptable position of the belt, and thus theaccelerometer. The control system is programmed to compare the measuredinferior/posterior distance to a predetermined distance, or distances,and provide output depending on how far the belt has moved in theinferior/posterior axis. The control system is programmed to provideoutput, depending on the calculated distance, to the CPR provider, or toother components of the system, and is also programmed to controloperation of the belt in response to the determined distance.

For example, upon detection of slight slippage, which is inevitable andnot of concern (in the range of 1 to 2 cm), the control system canoperate the display on the platform to provide a visual display element,including text or an icon, to indicate that the belt inferior/posteriorposition is within a nominal range of deviation from the originalposition.

Upon detection of significant inferior/posterior movement, which exceedsthe nominal range of movement but is not presumptively a sign ofdefective operation, the control system operates the display to providea visual display element, or operate a speaker to provide an audibleprompt, indicating that the belt has moved a sufficient distance towarrant inspection and confirmation that the belt is still appropriatelyplaced.

Upon detection of excessive inferior/posterior movement, which exceedsthe nominal range to the degree that it is presumptively a sign ofunacceptable slippage of the belt toward the abdomen or throat of thepatient, the control system is programmed to operate the display toprovide a visual display element, or operate a speaker to provide anaudible prompt, to communicate to the operator that significantinferior/posterior movement has been detected. Additionally, the controlsystem is programmed to stop operation of the belt tensioning mechanismsand return the system to a safe state, such as complete relaxation ofthe belt. The control system may also be programmed to take intermediatesteps, such as adjusting the depth of compression to accomplishcompression to a depth lesser than or greater than the recommended 1.5to 2 inches (3.75 to 5 cm), and/or (4) adjust the compression wave formor compression rate.

Upon detection of excessively asymmetrical or non-uniformanterior/posterior movement, which exceeds the nominal range to thedegree that it is presumptively a sign of unacceptable non-uniformity ofthe downward motion of the belt, the control system is programmed tooperate the display to provide a visual display element, or operate aspeaker to provide an audible prompt, to communicate to the operatorthat significant non-uniform motion has been detected. Additionally, thecontrol system may be programmed to stop operation of the belttensioning mechanisms and return the system to a safe state, such ascomplete relaxation of the belt. The control system may also beprogrammed to take intermediate steps, such as adjusting the depth ofcompression to accomplish compression to a depth lesser than or greaterthan the recommended 1.5 to 2 inches (3.75 to 5 cm), and/or (4) adjustthe compression wave form or compression rate.

Upon detection of significant non-uniformity of the downward motion ofthe belt, which exceeds the nominal range of movement but is notpresumptively a sign of defective operation, the control system isprogrammed to operate the display to provide a visual display element,or operate a speaker to provide an audible prompt, indicating that thebelt attained a non-uniform downward movement significant to warrantinspection and confirmation that the belt is still appropriately placedthat the system is operating properly and the patient is responding asexpected.

For both slip detection and non-uniformity detection, the control systemof the device can be programmed to control operation of the belt inresponse to the detected movement of the belt, and to control operationof any associated display or audio output to provide various advisoryoutputs in addition to those mentioned above. For horizontal slipdetection, only a single accelerometer is needed. For detection ofnon-uniform downward movement, two or more accelerometers may be used.When more accelerometers are used, a finer determination of the shape ofthe chest during compression can be obtained.

The systems have been described in the context of the CPR compressiondevice similar to the AutoPulse® CPR compression device which uses theload distributing band, with emphasis on detection of slippage. Thearrays can also be applied to other automated or motorized chestcompression belt systems, such as the system proposed in Lach,Resuscitation Method and Apparatus, U.S. Pat. No. 4,770,164 (Sep. 13,1988). Also, the device is illustrated with the commercially implementeddrive spool and motor as the means for tightening the belt about thechest and thorax of the patient. The system described above can be usedwith this and any other means for tightening the belt about the chestand thorax of the patient, including the numerous mechanisms disclosedin Lach and related patents such as Kelly, Chest Compression Apparatusfor Cardiac Arrest, U.S. Pat. No. 5,738,637.

In the LUCAS™ system (described in U.S. Pat. No. 7,569,021), the pistonis rigidly locked in place relative to the back plate, so like thesystem of FIGS. 3 and 4, a support structure which is fixed relative tothe base structure of the patient can be used to support one of thearrays. The rigid legs described by U.S. Pat. No. 7,569,021 may be usedas the support structure for the array. The necessary markers orcorresponding second emitter/detector array can be placed on thepatient's chest, in an electrode assembly the will be used fordefibrillation, or in a separate array, or on the outer edge of thepiston itself. The system can be applied to piston-based systems, suchas the LUCAS™ CPR chest compression system, to detect undesired tilt ofthe system during use, or migration of the piston relative to the targetarea of the sternum. This application is illustrated in FIGS. 13 and 14which show the LUCAS™ system in which a piston 31 and piston drivingmechanism 32 are suspended on support arms 33, and the support arms arefixed to a rigid backboard 34. The space between the piston and thebackboard accommodates a cardiac arrest patient. When initiallyinstalled on a patient, the piston is aligned vertically, and thecompression pad 35 lower surface, which impinges upon the chest of thepatient, is horizontal. The entire device is subject to tilting afterinitial placement. With accelerometers mounted on the compression pad,with the accelerometers disposed along the inferior/superior axis, forexample with one accelerometer 36 (FIG. 14) disposed inferiorly to asecond accelerometer 37, each with an axis of sensitivity aligned withthe inferior/superior axis and the anterior/posterior axis, the controlsystem can determine the orientation of the compression pad anddetermine whether the compression pad has deviated from its originalhorizontal orientation, and control the device or an associated displayor audio output in a manner similar to that described above in relationto the compression belt system. A deviation from horizontal orientationcan be determined based on acceleration data regarding upward anddownward movement of the accelerometers (and, hence, the inferior andsuperior portions of the compression pad). A deviation greater than 5°(degrees of departure from horizontal) from the orientation uponinitiation of the system, determined by comparing the downward distancetraversed by each accelerometer (calculated from the accelerationsignal), would, for example, result in operation of the control systemto present warnings to an operator, while deviation greater than 10°would result in operation of the control system to suspend compressiveoperation of the piston.

Referring again to the embodiments of FIGS. 3, 4, 5, 6 and 7, thesedevices can be used to implement a method of controlling the automatedchest compression devices based on the initial shape of the patient andon changing compliance of the patient over an extensive course of CPRcompressions. Some patients have relatively flat ribcages, asillustrated in FIG. 15, while other patients are barrel chested, andhave relatively round ribcages, as shown in FIG. 16. The barrel chestedpatient may require deeper compressions than the flat chested patient,and the flat chested patient may be successfully revived, with lowerrisk of iatrogenic injury, with more shallow chest compressions(vis-à-vis the barrel chested patient or the average patient).Accordingly, the chest compression devices of FIGS. 15 and 16 includeall the components of the devices of FIGS. 3 and 4, or FIGS. 5, 6 and 7and can be operated, through the computerized control system, todetermine the initial shape of the patient's shape by measuring thedistance from the gantry or backboard emitter/detectors 19 andassociated emitter/detectors 21 on the compression belt 3. The controlsystem is programmed to calculate the general shape of the patientdisposed within the belt, and thereafter operate the compression belt toprovide compressions of differing extent dependent on the general shapeof the patient (as computed from input from the sensors). (Our priorU.S. Pat. No. 6,616,620 provided for adjusting the compression depthachieved by the system based on the circumference of the patient, asdetermined by calculating the paid out length of the belt after slacktake-up). The control system may be programmed to determine theanterior/posterior thickness of the patient's chest, and determinewhether the patient is barrel chested, normal, or flat-chested, based onthe anterior/posterior thickness of the patient's chest. For a morerigorous analysis, the control system can be programmed to determine theactual shape of the anterior surface of the chest, and determine thatthe patient is typical or barrel-chested based on the calculated shapeof the patient's chest.

For example, a generally accepted goal for compression depth is 1.0 to2.0 inches (2.5 cm to 5 cm). For patients with unusually round thorax,that goal can be adjusted to 1.5 to 2.5 inches (4 cm to 6.4 cm). This isaccomplished by programming the control system to operate the motor soas to spool more of the belt during compressions strokes, upon detectionof a barrel chested patient.

In addition to altering the depth of compression achieved during thecompression stroke, the control system can also be programmed to adjustthe initial shape of the bladder (item 8 in Figures) upon detecting athoracic shape, such as a flat thorax shown in FIG. 15. FIG. 17illustrates use of the chest compression device in combination with thedistance sensors and an adjustable bladder disposed between thecompression belt and the patient. In this system, the bladder isoperated in a static mode (that is, it is not cyclically inflated in adynamic manner to cause chest compressions, but is filled and/orinflated prior to compressions and thereafter maintains a static volume(excepting minimal leakage and some slight compression) that modifiesthe forces applied by the compression belt). Adjustment of the initialshape of the bladder can be accomplished by providing a pump 38, apressure sensor 39 in fluid communication with the bladder and/or pumpand a check valve at the outlet of the pump and a vent valve fordeflating the bladder when desired. The operation of the pump, checkvalve 40 and vent valve 41 can all be controlled by the control systemin response to the data derived from the emitter/detectors and thepressure sensor. As an example, for patients of average size and shape,the bladder may be used as described in U.S. Pat. No. 6,616,620, as astatic bladder of a generally flat configuration when relaxed. Forpatients with a more shallow thorax, the bladder may be inflated to acylindrical shape, extending the combined height of the bladder and thepatient's chest (most conveniently, co-extensive with the chestcompression belt or load distributing panels of the load distributingband).

The method of operation can be applied to patient in a piston system,such as that shown in FIGS. 13 and 14, with the addition of an array ofemitter/detectors on the patient and the gantry of the piston-basedcompression device. Control systems may be employed with thesepiston-based systems analyze sensor input, calculate patient shape, andoperate the piston to achieve compressions to a depth dependent on thepatient shape, according to predetermined parameters of patient shape.

Referring back to FIGS. 9 and 10, the chest compression device fittedwith accelerometers to detect slippage can also be augmented todetermine changes in chest compliance versus depth of compression. Whenthe chest becomes excessively compliant, this the compressions may havecracked the patient's ribs or sternum. While fractures are a necessaryand acceptable incident of CPR, the effectiveness of CPR may decrease ifthe number of fractures degrades the resiliency of the chest.Accordingly, it may be desirable to decrease the force and depth ofautomated compressions when the resilience of the chest drops. To detecta drop in chest wall resilience, the pressure applied by the device tothe chest, or some proxy, such as pressure in the bladder, or pressurein additional bladders, may be monitored and compared to the measuredcompression depth. When compressing a patient with an intact rib cage,the initial pressure/depth ratio should be relatively high. If severalribs are broken during the course of CPR, the pressure needed tocompress to the desired depth should decrease abruptly.

FIG. 18 illustrates a system similar to that of FIGS. 9 and 10, with theadditional features to detect changes in chest resilience. The systemcan detect the pressure applied to the chest by detecting the pressurein the bladder 8 or additional bladders 42 disposed on the compressionbelt. Other means for detecting the force applied to the chest, or theresistance provided by the chest to further compression, including theload cell disclosed in U.S. Pat. No. 7,270,639, disposed under the backof the patient, torque sensors operably attached to the motor thatdrives the system, and strain gauges in the belt, piezo-electric sensorsin the belt, and other suitable sensors, can be used in place ofpressure sensors. FIG. 19 is a graph illustrating the relationshipbetween chest resilience and compression depth. The upper curveillustrates the expected relationship between chest resilience versuscompression depth. As expected, chest resilience (as indicated bybladder pressure or other indicator, is significant at the start of acompression, and increases with the depth of the compression. This isshown in the upper curve. Over the course of many compressions, chestresilience is expected to drop, but excessive loss of resilience such asthat illustrated in the lower curve should be addressed by the system oran operator.

Through the use of multiple pairs of pressure and displacement sensors,resilience can be measured at multiple locations along the extent of theinterface between the load distributing band and the patient surface.This is important as force is also distributed along theinferior/superior length of that interfacial surface, and rib fracturesoccur at specific locations along the ribs. Multiple sensors will allowfor a more precise localization of where the fracture occurs, which initself may be helpful to the rescuer, or may provide information for thecontrol system which may be programmed to adjust the compressionparameters to maximize hemodynamics whilst minimizing injury to thatspecific fracture location. This may be accomplished by having multipleinflatable bladders on the compression belt that can be inflated ordeflated to alleviate undue pressure to that particular injury location.

To address this issue of a decrease in chest wall resilience, andcontinue providing effective compressions, the control system candecrease the applied compression force, and decrease the spooling of thebelt to achieve a lesser compression depth, when a fall-off ofresistance v. depth change is detected. Thus, for example, peak bladderpressure of 2 psi (0.138 bar) may be normal, especially at the start ofcompressions. With the compression device operating normally to achieve2 inches (5 cm) of compression depth, a drop off of peak bladderpressure to 1 psi (0.069 bar) might indicate a change in chestresilience due to broken ribs. The baseline resilience for a particularpatient is calculated at the initiation of compressions, with monitoringfor changes over time. The numbers expressed above are merelyillustrative. The control system can be programmed such that, if such achange is detected by the pressure sensors and the control system, thecontrol system may operate the compression belt to provide a lesserdepth of compression, such as 1.1 inches (2.8 cm). This will provideadequate compressions, though less than ideal, which will limit furtherrib fractures which would make continued compressions at any levelineffective. The control system can also be programmed such that, ifbroken ribs are detected, the control system may operate the compressionbelt to accomplish the compression stroke over a longer time period,which would lead to lower compression velocity and minimize risk offurther fractures. The compression stroke could be lengthened from thecurrently preferred 200 milliseconds to 300 milliseconds, and thecompression rate could be lowered from the preferred 80 compression persecond to 50-60 compressions per minute.

While the preferred embodiments of the devices and methods have beendescribed in reference to the environment in which they were developed,they are merely illustrative of the principles of the inventions. Theelements of the various embodiments may be incorporated into each of theother species to obtain the benefits of those elements in combinationwith such other species, and the various beneficial features may beemployed in embodiments alone or in combination with each other. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

1-22. (canceled)
 23. A system for performing cardiopulmonaryresuscitation (CPR) on a patient, the system comprising: a housingproviding a platform adapted to be disposed under the thorax of thepatient during CPR; an automated chest compressor coupled to the housingand configured to provide chest compressions to the patient; two or moresensors attached to the automated chest compressor and configured togenerate data indicative of movement of the automated chest compressorrelative to the thorax of the patient; and a controller configured to:instruct the automated chest compressor to compress the thorax of thepatient at a resuscitative rate and depth, receive the data indicativeof the movement of the automated chest compressor, calculate apositioning of the automated chest compressor based on the receiveddata, detect movement of the automated chest compressor in aninferior/superior axis based on the calculated positioning; and anoutput communicatively coupled to the controller that provides feedbackbased on the detected movement of the automated chest compressor in theinferior/superior axis.
 24. The system of claim 23, wherein the outputis communicatively coupled to the controller and configured to providealerts in response to the detected movement of the automated chestcompressor in the inferior/superior axis by the controller.
 25. Thesystem of claim 24, wherein upon detection of movement of the automatedchest compressor in the inferior/superior axis, the controller isfurther configured to implement at least one of: (i) suspendcompressions of the automated chest compressor (ii) adjust a depth ofcompression and/or a rate of compression of the automated chestcompressor, and (iii) adjust a compression waveform to account for thedetected movement of the automated chest compressor in theinferior/superior axis.
 26. The system of claim 23, wherein thedetection of movement of the automated chest compressor in theinferior/superior axis includes detection of at least one of: unwantedmovement of the automated chest compressor and unwanted movement of thepatient on the housing.
 27. The system of claim 26, wherein thecontroller is further configured to calculate an amount of movement ofthe automated chest compressor from an original position based on thereceived data from the two or more sensors.
 28. The system of claim 27,wherein the controller is further configured to compare the calculatedamount of movement of the automated chest compressor to a predeterminedvalue to determine if the amount of movement exceeds a nominal range ofmovement.
 29. The system of claim 28, wherein the nominal range ofmovement along the inferior/superior axis of the patient is betweenapproximately 1.25 centimeters and 2.5 centimeters.
 30. The system ofclaim 23, wherein the automated chest compressor comprises a compressionbelt and a belt tensioner configured to tighten the compression beltaround the thorax of the patient in order to compress the thorax of thepatient at the resuscitative rate.
 31. The system of claim 30, whereinthe controller is configured to detect slippage of the compression beltalong the inferior/superior axis, the detection of the slippage beingindicative of movement of the compression towards the compressionwaveform abdomen or the head of the patient during the chestcompressions.
 32. The system of claim 23, wherein the controller detectsslippage of the automated chest compressor along the inferior/superioraxis, the detection of the slippage being indicative of movement of thecompression towards the abdomen or the head of the patient during thechest compressions.
 33. The system of claim 23, wherein the two or moresensors include at least one of optical emitters, ultrasound emitters,and Radio Frequency Identification (RFID) emitters.
 34. The system ofclaim 33, wherein the housing includes at least 3 three detectors todetect signals being generated by the emitters, and the controller isconfigured to perform a basic triangulation to determine a location ofthe automated chest compressor.
 35. The system of claim 23, wherein thetwo or more sensors include at least two accelerometers.
 36. The systemof claim 35, wherein the at least two accelerometers are three-axisaccelerometers.
 37. The system of claim 23, wherein the controller isfurther configured to detect non-uniform movement of the automated chestcompressor in response to the received data indicative of the movementof the automated chest compressor.
 38. The system of claim 37, whereinthe controller is further configured to generate one or more prompts toa CPR provider to indicate the non-uniform movement of the automatedchest compressor is detected.
 39. The system of claim 23, wherein theautomated chest compressor is a piston-based system that comprises: apiston, a piston driver structure, which includes arms for supportingthe piston and piston driver, and a compression pad that is affixed tothe piston.
 40. The system of claim 39, wherein the controller isconfigured to detect migration of the piston relative to a target areaof the thorax of the patient, the migration being indicative that thepiston has moved toward the abdomen or head of the patient during thechest compressions.
 41. The system of claim 39, wherein the two or moresensors include accelerometers that are affixed to the piston andgenerate acceleration data.
 42. The system of claim 41, wherein thecontroller detects a deviation from an original horizontal orientationbased on changes in the acceleration data from the two or more sensorsaffixed to the piston, said deviation being an indication of migrationof the piston from the target area of the thorax of the patient.
 43. Thesystem of claim 42, wherein upon a deviation greater than five degreesfrom the original horizontal orientation, the controller generates anaudible or visual warning to an output device.
 44. The system of claim43, wherein upon a deviation greater than 10 degrees from the originalhorizontal orientation, the controller suspends operation of the piston.45. The system of claim 23, wherein the controller is configured todetect migration of the automated chest compressor relative to a targetarea of the thorax of the patient, the migration being indicative thatthe automated chest compressor has moved toward the abdomen or head ofthe patient during the chest compressions.
 46. The system of claim 24,wherein the output includes at least one of visual feedback on a displayor audible feedback on a speaker.
 47. The system of claim 24, whereinthe output includes at least one of visual feedback on a display oraudible feedback on a speaker.